Re: [PATCH 18/45] writeback: introduce wait queue for balance_dirty_pages()

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Oct 08, 2009 at 01:59:07PM +0800, KAMEZAWA Hiroyuki wrote:
> On Thu, 8 Oct 2009 12:01:36 +0800
> Wu Fengguang <fengguang.wu@intel.com> wrote:
> 
> > On Thu, Oct 08, 2009 at 10:40:37AM +0800, KAMEZAWA Hiroyuki wrote:
> > > Thank you for clarification.
> > > Then, hmm, %iotwait (which 'top' shows) didn't work as desgined and we need
> > > to update throttle_vm_writeout() and some in vmscan.c. Thanks for input.
> > 
> > Thanks, you also reminds me to do io_schedule() in the nfs writeback
> > wait queue :)
> > 
> good side effect ;)

Done, hehe.

> > > BTW, I'm glad if I can know "how many threads/ios are throttoled now" per bdi.
> > 
> > Good suggestion. How about this patch?
> > 
> 
> Seems attractive. 
> Hmm..
> ==
> struct dirty_throttle_task {
> +	pid_t	owner_pid;
> ==
> and show it ? (too verbose ?

I even thought of adding the task pointer - it won't go away anyway :)

Thanks,
Fengguang

> 
> Regards,
> -Kame
> 
> > CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > ---
> >  fs/fs-writeback.c           |    1 +
> >  include/linux/backing-dev.h |    2 ++
> >  mm/backing-dev.c            |   33 +++++++++++++++++++++++++++++++++
> >  3 files changed, 36 insertions(+)
> > 
> > --- linux.orig/include/linux/backing-dev.h	2009-10-08 11:46:28.000000000 +0800
> > +++ linux/include/linux/backing-dev.h	2009-10-08 11:47:39.000000000 +0800
> > @@ -101,6 +101,7 @@ struct backing_dev_info {
> >  #ifdef CONFIG_DEBUG_FS
> >  	struct dentry *debug_dir;
> >  	struct dentry *debug_stats;
> > +	struct dentry *debug_throttle;
> >  #endif
> >  };
> >  
> > @@ -116,6 +117,7 @@ struct backing_dev_info {
> >  #define DIRTY_THROTTLE_PAGES_STOP	(1 << 22)
> >  
> >  struct dirty_throttle_task {
> > +	unsigned long		start_time;
> >  	long			nr_pages;
> >  	struct list_head	list;
> >  	struct completion	complete;
> > --- linux.orig/mm/backing-dev.c	2009-10-08 11:47:37.000000000 +0800
> > +++ linux/mm/backing-dev.c	2009-10-08 11:59:06.000000000 +0800
> > @@ -115,6 +115,23 @@ static int bdi_debug_stats_show(struct s
> >  	return 0;
> >  }
> >  
> > +static int bdi_debug_throttle_show(struct seq_file *m, void *v)
> > +{
> > +	struct backing_dev_info *bdi = m->private;
> > +	struct dirty_throttle_task *tt;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&bdi->throttle_lock, flags);
> > +	list_for_each_entry(tt, &bdi->throttle_list, list) {
> > +		seq_printf(m, "goal=%lukb\twaited=%lums\n",
> > +			   tt->nr_pages << (PAGE_SHIFT - 10),
> > +			   (jiffies - tt->start_time) * 1000 / HZ);
> > +	}
> > +	spin_unlock_irqrestore(&bdi->throttle_lock, flags);
> > +
> > +	return 0;
> > +}
> > +
> >  static int bdi_debug_stats_open(struct inode *inode, struct file *file)
> >  {
> >  	return single_open(file, bdi_debug_stats_show, inode->i_private);
> > @@ -127,15 +144,31 @@ static const struct file_operations bdi_
> >  	.release	= single_release,
> >  };
> >  
> > +static int bdi_debug_throttle_open(struct inode *inode, struct file *file)
> > +{
> > +	return single_open(file, bdi_debug_throttle_show, inode->i_private);
> > +}
> > +
> > +static const struct file_operations bdi_debug_throttle_fops = {
> > +	.open		= bdi_debug_throttle_open,
> > +	.read		= seq_read,
> > +	.llseek		= seq_lseek,
> > +	.release	= single_release,
> > +};
> > +
> >  static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
> >  {
> >  	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
> >  	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
> >  					       bdi, &bdi_debug_stats_fops);
> > +	bdi->debug_throttle = debugfs_create_file("throttle_list", 0444,
> > +						  bdi->debug_dir, bdi,
> > +						  &bdi_debug_throttle_fops);
> >  }
> >  
> >  static void bdi_debug_unregister(struct backing_dev_info *bdi)
> >  {
> > +	debugfs_remove(bdi->debug_throttle);
> >  	debugfs_remove(bdi->debug_stats);
> >  	debugfs_remove(bdi->debug_dir);
> >  }
> > --- linux.orig/fs/fs-writeback.c	2009-10-08 11:44:27.000000000 +0800
> > +++ linux/fs/fs-writeback.c	2009-10-08 11:47:39.000000000 +0800
> > @@ -284,6 +284,7 @@ static void bdi_calc_write_bandwidth(str
> >  void bdi_writeback_wait(struct backing_dev_info *bdi, long nr_pages)
> >  {
> >  	struct dirty_throttle_task tt = {
> > +		.start_time = jiffies,
> >  		.nr_pages = nr_pages,
> >  		.complete = COMPLETION_INITIALIZER_ONSTACK(tt.complete),
> >  	};
> >